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Organic chemistry, naming cycloalkenes

  1. Sep 26, 2013 #1
    1. The problem statement, all variables and given/known data

    organic.jpg

    2. Relevant equations



    3. The attempt at a solution

    Shouldnt the name for that be 3-fluoro-2-methyl cyclopentene instead of 4-fluoro-3-methyl cyclopentene ?, if not can someone explain to me why ?
     
  2. jcsd
  3. Sep 26, 2013 #2

    DrClaude

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    Staff: Mentor

    From the IUPAC rules:
     
  4. Sep 27, 2013 #3
    The carbon at the top, on the tip of the pentagon, because if you number clockwise from that carbon the methyl will be on the second carbon and the fluoroide on the third.
     
  5. Sep 27, 2013 #4

    DrClaude

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    Did you read the rule? Let me quote again: the double bond carbons are assigned ring locations #1 and #2. If you number the top carbon #1, then you have to go counter-clockwise for the other double-bond carbon to be #2.
     
  6. Sep 27, 2013 #5
    Oh, I see it now, so it should definately be 4-fluoro-3-methyl cyclopentene. Thanks for making it more clearer :approve:
     
  7. Sep 27, 2013 #6

    DrClaude

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    Just to add a further point of detail: if you take the top C to be #1 and go counter-clockwise, you get 4-fluoro-5-methyl cyclopentene. The nearest substituent rule then tells you to set the top C to #2 and count clockwise to get 4-fluoro-3-methyl cyclopentene.
     
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